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Tips on assessing fitness to fly

Aviation health specialist Dr Raymond Johnston gives his advice on ensuring patients fly safely and comfortably

Aviation health specialist Dr Raymond Johnston gives his advice on ensuring patients fly safely and comfortably

1 Understanding the physiology of flying helps reach a more objective conclusion about fitness. Modern aircraft have a cabin altitude between 5,000 and 8,000 feet which results in reduced barometric pressure (565mmHg) and a decrease in the partial pressure of alveolar oxygen (75mmHg).

But due to the shape of the oxy-haemoglobin dissociation curve, this only results in a fall of oxygen saturation to around 90%. This is well tolerated by most healthy travellers. But this decrease in saturation needs to be taken into consideration for those with cardiac and pulmonary conditions or indeed anaemia.

2 Understand the process. The final decision to carry a passenger is the airline's, but the more information that is provided – for example on a MEDIF form – the more likely it is that an evidence-based fair decision can be made.

An example of a Medif form can be found on British Airways website.

3 Applying that process to specific conditions. Knowing the challenges the cabin environment may pose simplifies the assessment of a passenger's fitness. This should avoid an adverse effect on the medical condition or the safe conduct of the flight.

4 Supplementary oxygen is not available routinely and needs to be requested in advance. Oxygen is available for emergency use by the cabin crew and drop-down oxygen for passengers in the case of decompression.

Most commercial airlines will supply medical oxygen when requested in advance and may charge.

5 Advise patients aspirin has not been shown to be effective thromboprophylaxis. On commercial flights, many passengers sit in confined spaces. This may reduce the opportunity to get up and walk about.

The potential for the development of travellers' thrombosis, particularly on flights of longer than four hours, should be borne in mind and the use of lower-limb exercises may be of value in improving the venous return. More specific prophylaxis requires an individual risk assessment. Aspirin has not been shown to be effective.

6 Most patients with cardiovascular disease can travel safely. Despite the physiological changes in the aircraft cabin, the majority of patients with cardiac conditions can travel safely as long as they are warned to carry their medications in their hand baggage. For example, patients with a recent myocardial infarction may travel after seven to 10 days if there are no complications.

If the patient has undergone an exercise test that shows no residual ischaemia or symptoms, this may be helpful, but is not a mandatory requirement.

7 Air travel should not be a problem for passengers with diabetes but pre-planning is important and discussion with the diabetic management team is essential.

All equipment and medication should be carried in hand baggage. The insulin not being used in flight should not be placed in hold baggage as the conditions may degrade insulin and baggage may be lost. Insulin can be carried in a coolbag for even the longest journey.

Patients should discuss their regime with their treating physician.

8 Jetlag (circadian dysrhythmia) may complicate the timing of medication, especially for patients with type 1 diabetes. Travelling east, the day will be shortened and, if by more than two hours, it may be necessary to take fewer units with intermediate or long-acting insulin.

Travelling west, the travel day will be extended and, if by more than two hours, it may be necessary to supplement this with additional injections of short-acting insulin or an increased dose of an intermediate.

Type 2 diabetes is not a problem for diet or oral medication, nor indeed for insulin as the endogenous insulin, which remains in type 2, will provide a suitable buffer and assist control. Further information can be found at

9 Reduced pressure causes gas to expand. Expansion can be as much as 30%, which may cause problems for the ear, giving rise to pain and possible perforation of the eardrum. Similar issues may occur following surgery, where gas is introduced.

10 Travelling in an aircraft cabin does not result in dehydration. There is no evidence of any change in osmolality. The aircraft environment has a low humidity, usually in the range of 10-20%, compared with 40-50% in most buildings. The low humidity particularly affects the mucous membranes.

The CAA's Aviation Health Unit has published a free downloadable guide on assessing a patient's fitness to fly.

Dr Raymond Johnston is head of the Aviation Health Unit at the UK Civil Aviation Authority

Pre-planning is essential for type 1 diabetes patients who travel

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